Kozai is a Python package to evolve hierarchical triples in the secular approximation. Hierarchical triples may be evolved either using the Delaunay formalism (Naoz et al. 2013b) or the vectorial formalism (Katz et al. 2011). The quadrupole, octupole, and hexadecapole terms of the Hamiltonian may be toggled to be included (or not) in the equations of motion. Post-Newtonian terms may also be toggled to include both relativistic precession (PN 1) and gravitational radiation (PN 2.5) using terms from Blaes et al. (2002).
The package provides a TripleDelaunay object which may be integrated using the Delaunay orbital elements and a TripleVectorial which may be integrated using the eccentricity and angular momentum vectors. This allows the integration to occur within the context of an external Python program.
The underlying integrator is from the SciPy ODE package. By default this package uses VODE as its integration algorithm, but the algorithm may be changed to any of the other integration algorithms supported by the SciPy ODE package.
The Kozai package is available on PyPI and can be installed with pip:
pip install kozai
Or, if you do not have the permissions to run the above:
pip install --user kozai
An IPython notebook tutorial is in the docs folder. The tutorial can be also be accessed online here.
Note that you will need to separately install matplotlib to run the tutorial
if you don't have it installed already. matplotlib will be installed if you
install the requirements-dev.txt file described below.
If you want to do any development on the kozai package it can help to install
the dependencies in the requirements-dev.txt file. If you are in the root
directory of the kozai repository you can do this as follows:
pip install -r requirements-dev.txt